Flexible organic light emitting display device with encapsulation film and dam and method of fabricating the same

ABSTRACT

A flexible organic light emitting display (OLED) device includes a flexible substrate having a display area, a non-display area at a periphery of the display area and a folding region; at least one organic emitting diode on the flexible substrate in the display area; an encapsulation film covering the organic emitting diode; and a dam on the flexible substrate. The dam laterally surrounds the display area and includes: a first dam in the folding region; and a second dam outside the folding region, wherein the average thickness of the first dam is smaller than the average thickness of the second dam.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of Korean Patent ApplicationNo. 10-2015-0150153 filed in the Republic of Korea on Oct. 28, 2015,which is hereby incorporated by reference.

BACKGROUND

Field of Technology

The present disclosure relates to an organic light emitting display(OLED) device, and more particularly, to a flexible OLED device.

Discussion of the Related Art

As information technology and mobile communication technology have beendeveloped, a display device capable of displaying a visual image hasalso been developed. Flat panel display devices, such as a liquidcrystal display (LCD) device and an OLED device, are developed and used.

Among these flat panel display devices, since the OLED device hasadvantages in response time, contrast ratio, viewing angle, powerconsumption, and so on, the OLED device is widely developed.

An emitting diode including an organic emitting layer is susceptible todamage from moisture. To prevent moisture penetration into the emittingdiode and protect the emitting diode from external impacts, anencapsulation substrate of glass is attached onto the emitting diode.

Recently, foldable, bendable or rollable display devices (hereinafter“flexible display device”) have been introduced.

In the flexible OLED device, an encapsulation film including aninorganic layer and an organic layer is used instead of theencapsulation substrate of glass. Namely, by using the encapsulationfilm for preventing moisture penetration into the emitting diode and toprotect the emitting diode, the display device has a flexible property.

FIG. 1 is a cross-sectional view of the related art flexible OLEDdevice.

Referring to FIG. 1, the related art flexible OLED device 1 includes aflexible substrate 10, an organic emitting diode D and an encapsulationfilm 20. A display area AA and a non-display area NA at a periphery ofthe display area AA are defined on the flexible substrate 10, and theorganic emitting diode D is disposed on the flexible substrate 10. Theencapsulation film 20 covers the organic emitting diode D.

The organic emitting diode D is disposed in the display area AA, and adriving part (not shown) driving the organic emitting diode D isdisposed in the non-display area NA.

Although not shown, the organic emitting diode D includes first andsecond electrodes, which faces each other, and an organic emitting layertherebetween. In addition, a switching thin film transistor (TFT) as aswitching element and a driving TFT as a driving element are formed ineach pixel region on the flexible substrate 10, and the first electrodeof the organic emitting diode D is connected to the driving TFT.

The encapsulation film 20 covers the organic emitting diode D andcorresponds to the display area AA and the non-display area NA, inparticular, overlaps both the display area AA and the non-display areaNA. The damages on the organic emitting diode D in a condition of hightemperature and high humidity are prevented by the encapsulation film20.

An inorganic layer and an organic layer are alternately stacked to formthe encapsulation film 20. For example, the encapsulation film 20 mayhave a triple-layered structure of a first inorganic layer 22 on theorganic emitting diode D, an organic layer 24 on the first inorganiclayer 22 and a second inorganic layer 26 on the organic layer 24.

However, when the flexible OLED device is operated under a condition ofhigh temperature and high humidity, the emitting diode is still damagedresulting in problems in display quality and a lifetime of the flexibleOLED device.

SUMMARY

Accordingly, the present invention is directed to a flexible OLED devicethat substantially obviates one or more of the problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a flexible OLED devicethat can operate at conditions of high temperature and high humidity.

Another object of the present invention is to provide a flexible OLEDdevice that has a high display quality and long lifetime.

Another object of the present invention is to provide a flexible OLEDdevice that can be easily manufactured with a low cost.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, aflexible OLED device comprises a flexible substrate including a displayarea, a non-display area at a periphery of the display area and afolding region, at least one organic emitting diode on the flexiblesubstrate in the display area; an encapsulation film covering theorganic emitting diode, a dam on the flexible substrate, wherein the damlaterally surrounds the display area and comprises a first dam in thefolding region and a second dam outside the folding region, wherein theaverage thickness of the first dam is smaller than the average thicknessof the second dam.

In another aspect, a method for manufacturing a flexible OLED devicecomprises providing a flexible substrate including a display area, anon-display area at a periphery of the display area and a foldingregion, forming a dam surrounding the display area on the flexiblesubstrate, wherein the dam comprises a first dam in the folding regionand a second dam outside the folding region, wherein the averagethickness of the first dam is smaller than the average thickness of thesecond dam, forming an emitting diode within the display area, coveringthe display area and the non-display area with a first inorganic layer,and covering the display area with an organic layer.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a cross-sectional view of the related art flexible OLEDdevice.

FIG. 2 is plane view illustrating a flexible OLED device according tofirst to fifth embodiments of the present invention.

FIG. 3 is a cross-sectional view taken along the line A-A′ of FIG. 2 andillustrating a flexible OLED device according to the first to thirdembodiments of the present invention.

FIG. 4 is a cross-sectional view taken along the line B-B′ of FIG. 2 andillustrating a flexible OLED device according to the first embodiment ofthe present invention.

FIG. 5 is a cross-sectional view taken along the line B-B′ of FIG. 2 andillustrating a flexible OLED device according to the second and thirdembodiments of the present invention.

FIG. 6 is a cross-sectional view taken along the line C-C′ of FIG. 2 andillustrating a flexible OLED device according to the second and thirdembodiments of the present invention.

FIG. 7A is a cross-sectional view taken along the line D-D′ of FIG. 2and illustrating a flexible OLED device according to the secondembodiment of the present invention.

FIG. 7B is a cross-sectional view taken along the line D-D′ of FIG. 2and illustrating a flexible OLED device according to the second andthird embodiments of the present invention.

FIG. 8 is a cross-sectional view taken along the line A-A′ of FIG. 2 andillustrating a flexible OLED device according to the fourth embodimentof the present invention.

FIG. 9 is a plane view illustrating a position of a spacer in a flexibleOLED device according to the fourth embodiment of the present invention.

FIG. 10 is a cross-sectional view taken along the line B-B′ of FIG. 2and illustrating a flexible OLED device according to the fourthembodiment of the present invention.

FIG. 11 is a cross-sectional view taken along the line C-C′ of FIG. 2and illustrating a flexible OLED device according to the fourthembodiment of the present invention.

FIG. 12 is a cross-sectional view taken along the line D-D′ of FIG. 2and illustrating a flexible OLED device according to the fourthembodiment of the present invention.

FIG. 13 is a plane view illustrating a flexible OLED device according tothe fifth embodiment of the present invention.

FIG. 14 is a cross-sectional view taken along the line D-D′ of FIG. 13.

FIG. 15 is a plane view illustrating a flexible OLED device according tothe sixth embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings.

FIG. 2 is plane view illustrating first to fifth embodiments of aflexible OLED device.

As shown in FIG. 2, an OLED device 100 of the present invention is aflexible display device being foldable, bendable or rollable along afolding region FR. For example, the folding region FR is defined along aminor axis of the flexible OLED device 100. Alternatively, the foldingregion FR may be defined along a major axis of the flexible OLED device100.

When the folding region FR is defined along the minor axis as shown inFIG. 2, a pad region (not shown) may be defined at at least one end ofthe major axis. In an alternative embodiment (not shown), if the foldingregion FR is defined along the major axis, the pad region may be definedat at least one end of the minor axis.

In the flexible OLED device 100, a plurality of pixel regions P aredefined in a display area AA on the flexible substrate 100, and anorganic emitting diode (not shown) is formed in each pixel region P.

In addition, a dam 170 is formed at a non-display area NA, which isdefined as a region at a periphery of the display area AA, to surroundthe display area AA.

Moreover, an encapsulation film (not shown) covering the organicemitting diode and the dam 170 is formed. Namely, the encapsulation filmcorresponds to the display area AA and the non-display area NA, inparticular overlaps the display area AA and the non-display area NA.

For example, the encapsulation film may have a triple-layered structureof a first inorganic layer, an organic layer on the first inorganiclayer and a second inorganic layer on the organic layer. In thisinstance, the organic layer is disposed inside the dam 170, and thefirst and second inorganic layers are disposed to cover the dam 170. Asa result, moisture penetration into the display area through a side ofthe organic layer of the encapsulation film is prevented.

Flow of the organic material, which is coated by a coating process, maybe blocked by the dam 170 such that the organic layer 182 is formedinside the dam 170. Accordingly, the side surface of the organic layer182 is not exposed such that problems in display quality and a lifetimeof the flexible OLED device by moisture penetration may be prevented.

FIG. 3 is a cross-sectional view taken along the line A-A′ of FIG. 2 andillustrating a flexible OLED device according to the first to thirdembodiments.

As shown in FIG. 3, the TFT Tr, the organic emitting diode D and theencapsulation film 180 are stacked over the flexible substrate 110.

For example, the flexible substrate 110 may be a substrate formed of apolymer, in particular, polyimide. For fabrication, a carrier substrate(not shown) may be attached to a lower surface of the flexible substrate110, elements such as the TFT Tr may be formed on the flexible substrate110, and the carrier substrate is released from the flexible substrate110. Thus, the carrier substrate may facilitate fabrication of the TFTTr.

The TFT Tr is formed on the flexible substrate 110. Although not shown,a buffer layer may be formed on the flexible substrate 110, and the TFTTr may be formed on the buffer layer.

A semiconductor layer 122 is formed on the flexible substrate 110. Thesemiconductor layer 122 may include an oxide semiconductor material orpolycrystalline silicon.

When the semiconductor layer 122 includes the oxide semiconductormaterial, a light-shielding pattern (not shown) may be formed under thesemiconductor layer 122. The light to the semiconductor layer 122 may beshielded or blocked by the light-shielding pattern such that thermaldegradation of the semiconductor layer 122 can be prevented. When thesemiconductor layer 122 includes polycrystalline silicon, impurities maybe doped into both sides of the semiconductor layer 122.

A gate insulating layer 124 is formed on the semiconductor layer 122.The gate insulating layer 124 may be formed of an inorganic insulatingmaterial such as silicon oxide or silicon nitride.

A gate electrode 130, which is formed of a conductive material, e.g.,metal, is formed on the gate insulating layer 124 above a center of thesemiconductor layer 122.

In FIG. 3, the gate insulating layer 124 is formed on the entire surfaceof the flexible substrate 110. Alternatively, the gate insulating layer124 may be patterned to have the same shape or a similar shape as thegate electrode 130.

An interlayer insulating layer 132, which is formed of an insulatingmaterial, is formed on an entire surface of the flexible substrate 110including the gate electrode 130. The interlayer insulating layer 132may be formed of an inorganic insulating material, e.g., silicon oxideor silicon nitride, or an organic insulating material, e.g.,benzocyclobutene or photo-acryl.

The interlayer insulating layer 132 includes first and second contactholes 134 and 136 exposing both sides of the semiconductor layer 122.The first and second contact holes 134 and 136 are positioned at bothsides of the gate electrode 130 to be spaced apart from the gateelectrode 130.

In FIG. 3, the first and second contact holes 134 and 136 extend intothe gate insulating layer 124. Alternatively, when the gate insulatinglayer 124 is patterned to have the same shape as the gate electrode 130,the first and second contact holes 134 and 136 are formed only throughthe interlayer insulating layer 132 and not through the gate insulatinglayer 124.

A source electrode 140 and a drain electrode 142, which are formed of aconductive material, e.g., metal, are formed on the interlayerinsulating layer 132. The source electrode 140 and the drain electrode142 are spaced apart from each other with respect to the gate electrode130 and respectively contact both sides of the semiconductor layer 122through the first and second contact holes 134 and 136.

The semiconductor layer 122, the gate electrode 130, the sourceelectrode 140 and the drain electrode 142 constitute the TFT Tr, and theTFT Tr serves as a driving element.

In FIG. 3, the gate electrode 130, the source electrode 140 and thedrain electrode 142 are positioned over the semiconductor layer 122.Namely, the TFT Tr has a coplanar structure. Alternatively, in the TFTTr, the gate electrode may be positioned under the semiconductor layer,and the source and drain electrodes may be positioned over thesemiconductor layer such that the TFT Tr may have an inverted staggeredstructure. In this instance, the semiconductor layer may includeamorphous silicon.

Although not shown, a gate line and a data line are disposed on or overthe flexible substrate 110 and cross each other to define a pixelregion. In addition, a switching element, which is electricallyconnected to the gate line and the data line, may be disposed on theflexible substrate 110. The switching element is electrically connectedto the TFT Tr as the driving element.

In addition, a power line, which is parallel to and spaced apart fromthe gate line or the data line, may be formed on or over the flexiblesubstrate 110. Moreover, a storage capacitor for maintaining a voltageof the gate electrode 130 of the TFT Tr during one frame, may be furtherformed on the flexible substrate 110.

A passivation layer 150, which includes a drain contact hole 152exposing the drain electrode 142 of the TFT Tr, is formed to cover theTFT Tr.

A first electrode 160, which is connected to the drain electrode 142 ofthe TFT Tr through the drain contact hole 152, is separately formed ineach pixel region. The first electrode 160 may be an anode and may beformed of a conductive material having a relatively high work function.For example, the first electrode 160 may be formed of a transparentconductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide(IZO).

When the organic emitting diode D is operated in a top-emission type, areflection electrode or a reflection layer may be formed under the firstelectrode 160. For example, the reflection electrode or the reflectionlayer may be formed of aluminum-paladium-copper (APC) alloy.

A bank layer 166, which covers edges of the first electrode 160, isformed on the passivation layer 150. A center of the first electrode 160in the pixel region is exposed through an opening of the bank layer 166.

An organic emitting layer 162 is formed on the first electrode 160. Theorganic emitting layer 162 may have a single-layered structure of anemitting material layer formed of an emitting material. Alternatively,to improve emitting efficiency, the organic emitting layer 162 may havea multi-layered structure including a hole injection layer, a holetransporting layer, the emitting material layer, an electrontransporting layer and an electron injection layer sequentially stackedon the first electrode 160.

A second electrode 164 is formed over the flexible substrate 110including the organic emitting layer 162. The second electrode 164 ispositioned at an entire surface of the display area. The secondelectrode 164 may be a cathode. The second electrode 164 may be formedof a conductive material having a lower work function than the firstelectrode 160. For example, the second electrode 164 may be formed ofaluminum (Al), magnesium (Mg) or Al—Mg alloy.

The first electrode 160, the organic emitting layer 162 and the secondelectrode 164 constitute the organic emitting diode D.

An encapsulation film 180 is formed on the organic emitting diode D toprevent penetration of moisture into the organic emitting diode D. Theencapsulation film 180 may have has a triple-layered structure of afirst inorganic layer 182, an organic layer 184 and a second inorganiclayer 186. However, it is not limited thereto.

For example, the encapsulation film 180 may further include an organiclayer on the second inorganic layer 186 or an organic layer and aninorganic layer stacked on the second inorganic layer 186.

The first inorganic layer 182 contacts and covers the organic emittingdiode D. For example, the first inorganic layer 182 may be formed of oneof silicon oxide (SiOx), silicon nitride (SiNx) and silicon-oxy-nitride(SiON).

The organic layer 184 is formed on the first inorganic layer 182. Thestress to the first inorganic layer 182 may be reduced by the organiclayer 184. For example, the organic layer 182 may be formed of anacryl-based material or an epoxy-based material.

The second inorganic layer 186 is formed on the organic layer 184 andmay be formed of one of silicon oxide (SiOx), silicon nitride (SiNx) andsilicon-oxy-nitride (SiON).

For example, each of the first and second inorganic layers 182 and 186may be formed by a plasma enhanced chemical vapor deposition (PECVD)process or an atomic layer deposition (ALD) process, and the organiclayer 184 may be formed by an inkjet coating process, a slit coatingprocess or a bar coating process.

Although not shown, a barrier film may be attached to the encapsulationfilm 180, and a polarization plate for reducing an ambient lightreflection may be attached to the barrier film. For example, thepolarization plate may be a circular polarization plate.

FIG. 4 is a cross-sectional view taken along the line B-B′ of FIG. 2 andillustrating a flexible OLED device according to the first embodiment.

As shown in FIG. 4, the organic emitting diode D is formed in thedisplay area AA of the flexible substrate 110, and the dam 170 is formedin the non-display area NA of the flexible substrate 110 to surround thedisplay area AA.

The dam 170 has a pre-determined thickness and is positioned to bespaced apart from the organic emitting diode D. The dam 170 may beformed of the same material and formed at the same layer as the banklayer 166. For example, the dam 170 may be formed of an inorganicmaterial, such as silicon oxide or silicon nitride, or an organicmaterial such as polyimide.

In addition, the encapsulation film 180 is formed to cover the organicemitting diode D and the dam 170. As mentioned above, the encapsulationfilm 180 may include the first inorganic layer 182, the organic layer184 and the second inorganic layer 186.

The first and second inorganic layers 182 and 186 cover the organicemitting diode D and the dam 170, and the organic layer 184 ispositioned inside the area surrounded by the dam 170. Namely, theorganic layer 184 covers the organic emitting diode D and does notoverlap the dam 170. In other words, the organic layer 184 has a widthor a plane area being smaller than each of the first and secondinorganic layers 182 and 186.

When the organic material is coated to form the organic layer 184 afterthe first inorganic layer 182 is deposited, the flow of the organicmaterial is blocked by the dam 170 such that the organic layer 184 isformed inside the area defined by the dam 170. Accordingly, the sidesurface of the organic layer 184 is completely covered by the secondinorganic layer 186 such that the moisture penetration through the sidesurface of the organic layer 184 is prevented.

The dam 170 has the substantially same height or thickness at the foursides of the flexible substrate 110.

FIG. 5 is a cross-sectional view taken along the line B-B′ of FIG. 2 andillustrating a flexible OLED device according to the second and thirdembodiments. FIG. 6 is a cross-sectional view taken along the line C-C′of FIG. 2 and illustrating a flexible OLED device according to thesecond and third embodiments.

As shown in FIGS. 5 and 6, the organic emitting diode D is formed in thedisplay area AA of the flexible substrate 210, and the dam 270 is formedin the non-display area NA of the flexible substrate 210 to surround thedisplay area AA. For example, the dam 270 may be formed of an inorganicmaterial, such as silicon oxide or silicon nitride, or an organicmaterial such as polyimide.

As explained through FIG. 3, the TFT Tr including the semiconductorlayer 122, the gate electrode 130, the source electrode 140 and thedrain electrode 142 is formed on the flexible substrate 110, and theorganic emitting diode D includes the first electrode 160, which isconnected to the drain electrode 142 of the TFT Tr, the second electrode164, which faces the first electrode 160, and the organic emitting layer162 therebetween.

In addition, the bank 166 covering the edge of the first electrode 160is formed at a boundary of the pixel region P.

Referring again to FIGS. 5 and 6, the dam 270 is spaced apart from theorganic emitting diode D and includes a first dam 270 a in the foldingregion FR and a second dam 270 b in other region, e.g., an unfoldingregion. The first dam 270 a has a thickness smaller than the second dam270 b.

For example, when the dam 270 is positioned at the same layer and isformed of the same material as the bank layer 166 (of FIG. 3), the firstdam 270 has a first thickness t1 being smaller than the bank layer 166and the second dam 270 has a second thickness t2 being greater than thefirst thickness t1 and being substantially equal to the bank layer 166.

Moreover, the encapsulation film 280, which may include the firstinorganic layer 282, the organic layer 284 and the second inorganiclayer 286, is formed to cover the organic emitting diode D and the dam270.

The first and second inorganic layers 282 and 286 cover the organicemitting diode D and the dam 270, and the organic layer 284 ispositioned inside the area surrounded by the dam 270. Namely, theorganic layer 284 covers the organic emitting diode D and does notoverlap the dam 270. In other words, the organic layer 284 has a widthor a plane area being smaller than each of the first and secondinorganic layers 282 and 286.

When the organic material is coated to form the organic layer 284, thecoating process of the organic material is started at a starting lineSL, which is defined with a pre-determined distance from the dam 270,and is ended at an ending line EL, which is defined with apre-determined distance from the dam 270 at an opposite end. Namely, thecoating process of the organic material is performed in an areasurrounded by the dam 270.

Accordingly, even though the first dam 270 may have a relatively smallthickness in the folding region FR, the flow of the organic material maybe sufficiently blocked by the dam 270 such that the organic layer 284is formed inside the area surrounded by the dam 270.

In addition, since the thickness of the first dam 270 a in the foldingregion FR is reduced, the stress applied to the first and secondinorganic layers 282 and 286 in the folding operation is decreased. As aresult, the damages on the first and second inorganic layers 282 and 286by the folding operation is minimized or prevented such that thedecrease of the moisture barrier property of the encapsulation film 280may be prevented.

When the thickness of the second dam 270 b positioned along a directionof the C-C′ line in FIG. 2 is small, the organic material may overflowthe dam 270 such that the organic material may be coated on the edge ofthe flexible substrate 210. In this instance, the pad region (not shown)for electrical connection with an outer driving circuit may be coveredby the organic material. Accordingly, it may be preferred that thesecond thickness t2 of the second dam 270 b may be greater than thefirst thickness t1 of the first dam 270 a.

FIG. 7A is a cross-sectional view taken along the line D-D′ of FIG. 2and illustrating a flexible OLED device according to the secondembodiment. FIG. 7B is a cross-sectional view taken along the line D-D′of FIG. 2 and illustrating a flexible OLED device according to thesecond and third embodiments.

As shown in FIG. 7A the dam 270 may have uniform first thickness t1 inthe folding region FR and may have uniform second thickness t2, which isgreater than the first thickness t1, in the unfolding region.

Alternatively, as shown in FIG. 7B, the dam 270 may have an unevensurface in the folding region FR to include a first portion having thefirst thickness t1 and a second portion having the second thickness t2.Namely, the dam 270 in the folding region Fr may include a convexportion and/or a concave portion.

In FIG. 7B, the second portion, which is thicker, has the same thicknessas the dam 270 in the unfolding region. Alternatively, the thickness ofthe second portion may be smaller than the dam 270 in the unfoldingregion.

Namely, in the present invention, an average thickness (=(t1+t2 (of FIG.7B))/2) of the first dam 270 a in the folding region FR is smaller thanan average thickness of the second dam 270 b in the unfolding regionsuch that the organic layer 284 is positioned inside the area surroundedby the dam 270 and the stress onto the encapsulation film 280 in thefolding region by the folding operation is minimized or prevented.

Accordingly, in the flexible OLED device 200 in the second and thirdembodiments, by preventing the exposure of the side surface of theorganic layer 284 and minimizing the folding stress on the encapsulationfilm 280, the damages on the organic emitting diode D is minimized orprevented.

FIG. 8 is a cross-sectional view taken along the line A-A′ of FIG. 2 andillustrating a flexible OLED device according to the fourth embodiment.FIG. 9 is a plane view illustrating a position of a spacer in a flexibleOLED device according to the fourth embodiment.

As shown in FIG. 8, the TFT Tr, the organic emitting diode D and theencapsulation film 380 are stacked over the flexible substrate 310.

For example, the flexible substrate 310 may be a substrate formed of apolymer, in particular, polyimide. For fabrication, a carrier substrate(not shown) may be attached to a lower surface of the flexible substrate310, elements such as the TFT Tr may be formed on the flexible substrate310, and the carrier substrate is released from the flexible substrate310. Thus, the carrier substrate may facilitate fabrication of the TFTTr.

The TFT Tr is formed on the flexible substrate 310. Although not shown,a buffer layer may be formed on the flexible substrate 310, and the TFTTr may be formed on the buffer layer.

The semiconductor layer 322 is formed on the flexible substrate 310. Thesemiconductor layer 322 may include an oxide semiconductor material orpolycrystalline silicon.

The gate insulating layer 324 is formed on the semiconductor layer 322.The gate insulating layer 324 may be formed of an inorganic insulatingmaterial such as silicon oxide or silicon nitride.

The gate electrode 330, which is formed of a conductive material, e.g.,metal, is formed on the gate insulating layer 324 above a center of thesemiconductor layer 322.

The interlayer insulating layer 332, which is formed of an insulatingmaterial, is formed on an entire surface of the flexible substrate 310including the gate electrode 330. The interlayer insulating layer 332may be formed of an inorganic insulating material, e.g., silicon oxideor silicon nitride, or an organic insulating material, e.g.,benzocyclobutene or photo-acryl.

The interlayer insulating layer 332 includes first and second contactholes 334 and 336 exposing both sides of the semiconductor layer 322.The first and second contact holes 334 and 336 are positioned at bothsides of the gate electrode 330 to be spaced apart from the gateelectrode 330.

The source electrode 340 and the drain electrode 342, which are formedof a conductive material, e.g., metal, are formed on the interlayerinsulating layer 332. The source electrode 340 and the drain electrode342 are spaced apart from each other with respect to the gate electrode330 and respectively contact both sides of the semiconductor layer 322through the first and second contact holes 334 and 336.

The semiconductor layer 322, the gate electrode 330, the sourceelectrode 340 and the drain electrode 342 constitute the TFT Tr, and theTFT Tr serves as a driving element.

Although not shown, a gate line and a data line are disposed on or overthe flexible substrate 310 and cross each other to define a pixelregion. In addition, a switching element, which is electricallyconnected to the gate line and the data line, may be disposed on theflexible substrate 310. The switching element is electrically connectedto the TFT Tr as the driving element.

In addition, a power line, which is parallel to and spaced apart fromthe gate line or the data line, may be formed on or over the flexiblesubstrate 310. Moreover, a storage capacitor for maintaining a voltageof the gate electrode 330 of the TFT Tr during one frame, may be furtherformed on the flexible substrate 310.

The passivation layer 350, which includes a drain contact hole 352exposing the drain electrode 342 of the TFT Tr, is formed to cover theTFT Tr.

The first electrode 360, which is connected to the drain electrode 342of the TFT Tr through the drain contact hole 352, is separately formedin each pixel region. The first electrode 360 may be an anode and may beformed of a conductive material having a relatively high work function.For example, the first electrode 360 may be formed of a transparentconductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide(IZO).

The bank layer 366, which covers edges of the first electrode 360, isformed on the passivation layer 350. A center of the first electrode 360in the pixel region is exposed through an opening of the bank layer 366.

A spacer 368 is formed on the bank layer 366.

Generally, when the organic emitting layer 362 of the organic emittingdiode D is formed by a thermal vapor deposition process using a finemetal mask, the organic emitting diode D may be damaged by the finemetal mask. For example, the fine metal mask contacts the organicemitting layer 362 such that the organic emitting layer 362 may bedamaged. Accordingly, with the spacer 368 on the bank layer 366, thedamage of the organic emitting diode D by the fine metal mask isprevented.

The spacer 368 may be formed only on a portion of the bank layer 366.Namely, referring to FIG. 9, the bank layer 366 has one single body tocompletly surround the pixel region P, while the spacers 368 areseparately formed on a portion of the bank layer 366. In other words, atleast two spacers 368 are spaced apart from each other such that theother portions of the bank layer 366 are exposed.

For example, four spacers 268, which are spaced apart from each other,may be disposed at four sides of each pixel region P. The spacer 368 maybe formed of polymer such as polyimide.

The organic emitting layer 362 is formed on the first electrode 360. Theorganic emitting layer 362 may have a single-layered structure of anemitting material layer formed of an emitting material. Alternatively,to improve emitting efficiency, the organic emitting layer 362 may havea multi-layered structure including a hole injection layer, a holetransporting layer, the emitting material layer, an electrontransporting layer and an electron injection layer sequentially stackedon the first electrode 360.

The second electrode 364 is formed over the flexible substrate 310including the organic emitting layer 362. The second electrode 364 ispositioned at an entire surface of the display area AA. The secondelectrode 364 may be a cathode and may be formed of a conductivematerial having a relatively low work function. For example, the secondelectrode 364 may be formed of aluminum (Al), magnesium (Mg) or Al—Mgalloy.

The first electrode 360, the organic emitting layer 362 and the secondelectrode 364 constitute the organic emitting diode D.

The encapsulation film 380 is formed on the second electrode 384 of theorganic emitting diode D to prevent penetration of moisture into theorganic emitting diode D. The encapsulation film 380 may have has atriple-layered structure of a first inorganic layer 382, an organiclayer 384 and a second inorganic layer 386. However, it is not limitedthereto.

For example, the encapsulation film 380 may further include an organiclayer on the second inorganic layer 386 or an organic layer and aninorganic layer stacked on the second inorganic layer 386.

The first inorganic layer 382 contacts and covers the organic emittingdiode D. For example, the first inorganic layer 382 may be formed of oneof silicon oxide (SiOx), silicon nitride (SiNx) and silicon-oxy-nitride(SiON).

The organic layer 384 is formed on the first inorganic layer 382, andthe stress to the first inorganic layer 382 is reduced by the organiclayer 384. For example, the organic layer 382 may be formed of anacryl-based material or an epoxy-based material.

The second inorganic layer 386 is formed on the organic layer 384 andmay be formed of one of silicon oxide (SiOx), silicon nitride (SiNx) andsilicon-oxy-nitride (SiON).

For example, each of the first and second inorganic layers 382 and 386may be formed by a plasma enhanced chemical vapor deposition (PECVD)process or an atomic layer deposition (ALD) process, and the organiclayer 384 may be formed by an inkjet coating process, a slit coatingprocess or a bar coating process.

Although not shown, a barrier film may be attached to the encapsulationfilm 380, and a polarization plate for reducing an ambient lightreflection may be attached to the barrier film. For example, thepolarization plate may be a circular polarization plate.

FIG. 10 is a cross-sectional view taken along the line B-B′ of FIG. 2and illustrating a flexible OLED device according to the fourthembodiment. FIG. 11 is a cross-sectional view taken along the line C-C′of FIG. 2 and illustrating a flexible OLED device according to thefourth embodiment. FIG. 12 is a cross-sectional view taken along theline D-D′ of FIG. 2 and illustrating a flexible OLED device according tothe fourth embodiment.

As shown in FIGS. 10 and 11, the organic emitting diode D is formed inthe display area AA of the flexible substrate 310, and the dam 370surrounding the display area AA is formed in the non-display area NA ofthe flexible substrate 310.

For example, the dam 370 may be formed of an inorganic material, e.g.,silicon oxide or silicon nitride, or an organic material, e.g.,polyimide.

The dam 370 is positioned to be spaced apart from the organic emittingdiode D. The dam 370 includes a first dam 370 a of a single-layeredstructure in the folding region FR and a second dam 370 b of adouble-layered structure in the unfolding region, i.e., the other regionexcept the folding region FR. The second dam 370 b may include a lowerlayer 372 and an upper layer 374.

Namely, the first dam 370 a has a first thickness t1, and the second dam370 b has a second thickness t2 being greater than the first thicknesst1. The lower layer 372 of the second dam 370 b may have substantiallythe same thickness as the first dam 370 a.

The first dam 370 a and the lower layer 372 of the second dam 370 b maybe positioned at the same layer and be formed of the same material asthe bank layer 366 (of FIG. 8), and the upper layer 374 of the seconddam 370 b may be positioned at the same layer and be formed of the samematerial as the spacer 368 (of FIG. 8).

In FIG. 12, the first dam 370 a in the folding region FR has thesingle-layered structure. Alternatively, dam patterns (not shown), whichare spaced apart from each other, may be formed on the first dam 370 a.The dam patterns may have a dot shape and be disposed at the same layeras the upper layer 374 of the second dam 370 b.

In addition, the encapsulation film 380 is formed to cover the organicemitting diode D and the dam 370.

As mentioned above, the encapsulation film 380 may have has atriple-layered structure of a first inorganic layer 382, an organiclayer 384 and a second inorganic layer 386.

Since the first dam 370 a in the folding region FR has a single-layeredstructure, the first inorganic layer 382 in the folding region FRcontacts an upper surface of the first dam 370 a, which is disposed atthe same layer as the bank layer 366, in the folding region FR. On theother hand, the first inorganic layer 382 in the unfolding regioncontacts an upper surface of the upper layer 374 of the second dam 370a, which is disposed at the same layer as the spacer 368.

In this instance, the first and second inorganic layers 382 and 386cover the organic emitting diode D and the dam 370, and the organiclayer 384 is positioned inside an area surrounded by the dam 370.Namely, the organic layer 384 covers and overlaps the organic emittingdiode D and does not cover and overlap the dam 370. In other words, theorganic layer 384 has a width and/or an area being smaller than each ofthe first and second inorganic layers 382 and 386.

As mentioned above, flow of the organic material, which is coated by acoating process, is sufficiently blocked by the dam 370 such that theorganic layer 382 is formed inside the dam 370. Accordingly, the sidesurface of the organic layer 382 is not exposed.

In addition, since a thickness of the first dam 370 a in the foldingregion FR is reduced, the stress applied to the first and secondinorganic layers 382 and 386 during the folding operation may bedecreased. Accordingly, the damages on the first and second inorganiclayers 382 and 386 by the folding operation may be minimized orprevented such that the decrease of the moisture barrier property of theencapsulation film 380 may be prevented.

Namely, in the present invention, the average thickness of the first dam370 a in the folding region FR is smaller than the average thickness ofthe second dam 370 b in the unfolding region and the organic layer 384is positioned inside the area surrounded by the dam 370 such that thestress to the encapsulation film 380 in the folding region FR by thefolding operation may be minimized or prevented.

Accordingly, in the flexible OLED device 300 according to the fourthembodiment, the exposure of the side surface of the organic layer 384 isprevented and the folding stress is minimized or prevented such that thedamage on the organic emitting diode D is prevented.

FIG. 13 is a plane view illustrating a flexible OLED device according tothe fifth embodiment, and FIG. 14 is a cross-sectional view taken alongthe line D-D′ of FIG. 13.

As shown in FIGS. 13 and 14, the OLED device 400 can be foldable,bendable or rollable. Namely, the OLED device 400 is a flexible displaydevice. For example, the folding region FR is defined along a minor axisof the flexible OLED device 400. Alternatively, the folding region FRmay be defined along a major axis of the flexible OLED device 400.

When the folding region FR is defined along the minor axis as shown inFIG. 13, a pad region (not shown) may be defined in at least one end ofthe major axis.

In the flexible OLED device 400, a plurality of pixel regions P aredefined in a display area AA on the flexible substrate 400, and anorganic emitting diode (not shown) is formed in each pixel region P.

As explained through FIG. 3, the TFT Tr including the semiconductorlayer 122, the gate electrode 130, the source electrode 140 and thedrain electrode 142 is formed on the flexible substrate 110, and theorganic emitting diode D includes the first electrode 160, which isconnected to the drain electrode 142 of the TFT Tr, the second electrode164, which faces the first electrode 160, and the organic emitting layer162 therebetween.

In addition, the bank 166 covering the edge of the first electrode 160is formed at a boundary of the pixel region P. The spacer 368 (of FIG.8) may be further formed on the bank layer 166.

The dam 470 covering the display area AA, where the organic emittingdiode D is formed, is formed in the non-display area NA at a peripheryof the display area AA.

The dam 470 is partially removed in the folding region FR such that atleast one dam pattern 476, which has a dot shape and is spaced apartfrom the dam 470 in the non-folding region, is formed. Namely, the dam470 is discontinuous.

FIG. 14 shows that each of the dam 470 and the dam pattern 476 has asingle-layered structure. Alternatively, each of the dam 470 and the dampattern 476 may have a double-layered structure being similar to thesecond dam 370 b (of FIG. 12). On the other hand, the dam 470 may have adouble-layered structure, while the dam pattern 476 may have asingle-layered structure.

The encapsulation film 380 (of FIG. 12) is formed to cover the organicemitting diode D and the dam 470. The encapsulation film 380 may havehas a triple-layered structure of a first inorganic layer 482, anorganic layer 384 (of FIG. 10) and a second inorganic layer 486.

The first and second inorganic layers 482 and 486 cover the organicemitting diode D and the dam 470, and the organic layer 384 ispositioned inside an area surrounded by the dam 470. Namely, the organiclayer 384 covers and overlaps the organic emitting diode D and does notcover and overlap the dam 470. In other words, the organic layer 384 hasa width and/or an area being smaller than each of the first and secondinorganic layers 482 and 486.

As mentioned above, flow of the organic material, which is coated by acoating process, may be sufficiently blocked by the dam 470 such thatthe organic layer 382 is formed inside the dam 470. Accordingly, theside surface of the organic layer 382 may be not exposed.

In the flexible OLED device 400 according to the fifth embodiment, sincethe dam patterns 476 are disposed to be spaced apart from each other, anaverage thickness of the dam 470 in the folding region FR is reduced.

Namely, the thickness of the dam 470 in the folding region FR is reducesuch that the stress applied to the first and second inorganic layers482 and 486 by the folding operation is decreased. Accordingly, thedamages on the first and second inorganic layers 482 and 486 by thefolding operation may be minimized or prevented such that the decreaseof the moisture barrier property of the encapsulation film 380 may beprevented.

In other words, in the present invention, the average thickness of thedam 470 in the folding region FR is smaller than the average thicknessof the dam 470 in the unfolding region and the organic layer 384 ispositioned inside the area surrounded by the dam 470 such that thestress to the encapsulation film 380 in the folding region FR by thefolding operation is minimized or prevented.

Accordingly, in the flexible OLED device 400 according to the fifthembodiment, the exposure of the side surface of the organic layer 384 isprevented and the folding stress is minimized or prevented such that thedamage on the organic emitting diode D is prevented.

FIG. 15 is a plane view illustrating a flexible OLED device according tothe sixth embodiment.

As shown in FIG. 15, the OLED device 500 can be foldable, bendable orrollable. Namely, the OLED device 500 is a flexible display device. Forexample, the folding region FR is defined along a minor axis of theflexible OLED device 500. Alternatively, the folding region FR may bedefined along a major axis of the flexible OLED device 500.

When the folding region FR is defined along the minor axis as shown inFIG. 15, a pad region (not shown) may be defined in at least one end ofthe major axis.

In the flexible OLED device 500, a plurality of pixel regions P aredefined in a display area AA on the flexible substrate 500, and anorganic emitting diode (not shown) is formed in each pixel region P.

As explained through FIG. 3, the TFT Tr including the semiconductorlayer 122, the gate electrode 130, the source electrode 140 and thedrain electrode 142 is formed on the flexible substrate 110, and theorganic emitting diode D includes the first electrode 160, which isconnected to the drain electrode 142 of the TFT Tr, the second electrode164, which faces the first electrode 160, and the organic emitting layer162 therebetween.

In addition, the bank 166 covering the edge of the first electrode 160is formed at a boundary of the pixel region P. The spacer 368 (of FIG.8) may be further formed on the bank layer 166.

The dam 570 covering the display area AA, where the organic emittingdiode D is formed, is formed in the non-display area NA at a peripheryof the display area AA.

The dam 570 is partially removed in the folding region FR such thatfirst and second dam patterns 576 a and 576 b, each of which has a dotshape and is spaced apart from the dam 570 in the non-folding region, isformed. The first and second dams 576 a and 576 b are spaced apart fromeach other and arranged in a zigzag shape.

All of the dam 570, the first dam pattern 576 a and the second dampattern 576 b have a single-layered structure or a double-layeredstructure. Alternatively, the dam 570 may have a double-layeredstructure, while the first and second dam patterns 576 a and 576 b mayhave a single-layered structure.

The encapsulation film 380 (of FIG. 12) is formed to cover the organicemitting diode D, the dam 570 and the dam pattern 576. The encapsulationfilm 380 may have has a triple-layered structure of a first inorganiclayer 382 (of FIG. 10), an organic layer 384 (of FIG. 10) and a secondinorganic layer 386 (of FIG. 10).

The first and second inorganic layers 382 and 386 cover the organicemitting diode D, the dam 570 and the dam pattern 576, and the organiclayer 384 is positioned inside an area surrounded by the dam 570 and thedam pattern 576. Namely, the organic layer 384 covers and overlaps theorganic emitting diode D and does not cover and overlap the dam 570 andthe dam pattern 576.

As mentioned above, flow of the organic material, which is coated by acoating process, may be sufficiently blocked by the dam 570 and the dampattern 576 such that the organic layer 382 is formed inside the dam 570and the dam pattern 576. Accordingly, the side surface of the organiclayer 382 is not exposed.

In the flexible OLED device 500 according to the sixth embodiment, sincethe dam patterns 576 including the first and second dam patterns 576 aand 576 b are disposed to be spaced apart from each other and arrangedin the zigzag shape, an average thickness of the dam 570, i.e., the dampattern 576, in the folding region FR is reduced.

Namely, the thickness of the dam 570 in the folding region FR is reducesuch that the stress applied to the first and second inorganic layers382 and 386 by the folding operation is decreased. Accordingly, thedamages on the first and second inorganic layers 382 and 386 by thefolding operation is minimized or prevented such that the decrease ofthe moisture barrier property of the encapsulation film 380 isprevented.

In other words, in the present invention, the average thickness of thedam 570 in the folding region FR is smaller than the average thicknessof the dam 570 in the unfolding region and the organic layer 384 ispositioned inside the area surrounded by the dam 570 such that thestress applied to the encapsulation film 380 in the folding region FR bythe folding operation may be minimized or prevented.

Accordingly, in the flexible OLED device 500 according to the sixthembodiment, the exposure of the side surface of the organic layer 384may be prevented and the folding stress is minimized or prevented suchthat the damage on the organic emitting diode D may be prevented.

What is claimed is:
 1. A flexible organic light emitting display (OLED)device, comprising: a flexible substrate comprising: a display area; anon-display area at a periphery of the display area; a non-foldingregion; and a folding region; at least one organic emitting diode on theflexible substrate in the display area; an encapsulation film coveringthe organic emitting diode; and a dam on the flexible substrate, the damlaterally surrounding the display area and comprising: a first dam inthe folding region, and absent in the non-folding region; and a seconddam in the non-folding region, and absent in the folding region,wherein, in a direction perpendicular to a top surface of the flexiblesubstrate, an average thickness of the first dam is smaller than theaverage thickness of the second dam, wherein the first dam and thesecond dam are disposed on a same layer, and wherein a lower surface ofthe first dam and a lower surface of the second dam have a same heightfrom the flexible substrate in the perpendicular direction.
 2. Theflexible OLED device according to claim 1, wherein the encapsulationfilm comprises: a first inorganic layer; an organic layer on the firstinorganic layer; and a second inorganic layer on the organic layer,wherein the dam laterally surrounds the organic layer, and wherein thefirst inorganic layer and the second inorganic layer cover the dam. 3.The flexible OLED device according to claim 1, wherein each of the firstdam and the second dam has a respective constant thickness.
 4. Theflexible OLED device according to claim 1, wherein: the first damcomprises a first portion having a first thickness and a second portionhaving a second thickness; and the first thickness is smaller than thesecond thickness.
 5. The flexible OLED device according to claim 4,wherein the first dam comprises a convex portion and/or a concaveportion.
 6. The flexible OLED device according to claim 4, wherein thesecond portion of the first dam has a same thickness as the second dam.7. The flexible OLED device according to claim 4, wherein the secondportion of the first dam has a smaller thickness than the second dam. 8.The flexible OLED device according to claim 1, wherein: the first damincludes a single layer; and the second dam includes a lower layer andan upper layer.
 9. The flexible OLED device according to claim 8,wherein the lower layer of the second dam and the first dam are onecontinuous layer.
 10. The flexible OLED device according to claim 8,further comprising: a bank layer surrounding each of a plurality ofpixel regions defined in the display area; and at least one spacer onthe bank layer, wherein the first dam is positioned at a same layer asthe bank layer, wherein the lower layer of the second dam is positionedat the same layer as the bank layer, and wherein the upper layer of thesecond dam is positioned at a same layer as the spacer.
 11. The flexibleOLED device according to claim 1, wherein the first dam continuouslycovers the flexible substrate.
 12. The flexible OLED device according toclaim 1, wherein the first dam is partially removed and comprises dampatterns adapted for blocking flow of an organic material out of thedisplay area.
 13. The flexible OLED device according to claim 12,wherein the dam patterns comprise first dam patterns and second dampatterns spaced apart from each other and arranged in a zigzag shape.14. A method of fabricating a flexible organic light emitting displaydevice, comprising: providing a flexible substrate comprising: a displayarea; a non-display area at a periphery of the display area; anon-folding region; and a folding region; forming a dam surrounding thedisplay area on the flexible substrate, the dam comprising: a first damin the folding region, and absent in the non-folding region; and asecond dam in the non-folding region, and absent in the folding region,an average thickness of the first dam being smaller than an averagethickness of the second dam in a direction perpendicular to a topsurface of the flexible substrate; forming an emitting diode within thedisplay area; covering the display area and the non-display area with afirst inorganic layer; and covering the display area with an organiclayer, wherein a lower surface of the first dam and a lower surface ofthe second dam have a same height from the flexible substrate in theperpendicular direction.
 15. The method according to claim 14, furthercomprising: forming a second inorganic layer on the organic layer,wherein the dam laterally surrounds the organic layer, and wherein thefirst inorganic layer and the second inorganic layer cover the dam. 16.The method according to claim 14, wherein: the first dam comprises afirst portion having a first thickness and a second portion having asecond thickness; and the first thickness is smaller than the secondthickness.
 17. The method according to claim 16, wherein the secondportion of the first dam has a same thickness as the second dam.
 18. Themethod according to claim 16, wherein the second portion of the firstdam has a smaller thickness than the second dam.
 19. The methodaccording to claim 14, wherein: the first dam includes a single layer;and the second dam includes a lower layer and an upper layer.
 20. Themethod according to claim 14, wherein the first dam is partially removedand comprises dam patterns adapted for blocking flow of an organicmaterial out of the display area.